Methods for preventing a chytrid infection in a culture of Haematococcus pluvialis using hydrogen peroxide

Methods of treating contamination, particularly fungal contamination, in cultures of Haematococcus pluvialis with hydrogen peroxide are described herein. The method comprises detecting the contamination and then dosing the culture with a concentration of hydrogen peroxide based on the stage of the cells in the culturing process and at a frequency to increase the likelihood of the cells surviving until the process of accumulating carotenoids, such as astaxanthin, is complete.